656 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
earliest dated example of the evidence of false work is part of the 
foundations of Caligula’s palace,* and he mentions” also a facing of 
opus reticulatum and brick, which may very well be of the same 
period, as being very roughly executed, which would be natural if 
an attempt had been made to apply the new discovery to a purpose 
to which it was not suited. 
In the matter of arches and vaults, the later Romans believed that 
they had learned the art of building them from their old neighbors 
and enemies, the Etruscans; and probably they did, though it is easy 
to see that the character of the materials they had at hand was such 
as to favor an arched system, while the nature of the site of Rome 
and the surrounding country suggested the construction of drains 
and aqueducts, in which arching, to say the least, came in very use- 
fully. The history of Roman architecture in early and Republican 
times may, perhaps, never be recovered. The difficulties in the way 
of excavations are great, while, owing to the continuous occupation 
of sites, the results rarely throw much light on early work. There 
are some remains of early walls of that squared and bonded masonry 
which Vitruvius seems to have thought was one of the things Roman 
architects had borrowed from the Greeks,’ and we may assume as 
certain that, like the Etruscans, the Romans early used the arch to 
span gateways. But we do not know how soon they began to put 
the arch to other uses, and the extent to which vaulting was de- 
veloped, before it was taken up by the architects of the imperial 
period, is not altogether clear. The little dome over the ancient sub- 
terranean chamber, called the Tullianum in Rome, is built of cut stone 
in horizontal courses, and M. Chedanne declared? that the dome 
of the Pantheon is built entirely of brick in the same way—that is, 
in horizontal courses. If he was right, it would seem to indicate that 
even in the reign of Hadrian the Romans had not arrived at our con- 
ception of domes as developments of the arch and dependent for 
their stability on much the same forces, but they regarded them as 
systems of corbelling. The chamber above the Tulhanum, called the 
Mamertine prison, is, however, roofed with a small barrel vault neatly 
built with stone voussoirs (pl. 1, fig. 1). Its date is uncertain except 
that is very early Republican. If Vitruvius knew how to build a 
vault at all, it is surprising that he did not give instructions in the 
art in a work which he evidently intended should cover the whole 
field of building and in which he deals with so many smaller mat- 
ters. In the chapter on baths’ he twice mentions Camere, that is, 
@Remains, I, 196. @Op. cit. 
ob Tbid., II, 149. CNV. Vey 0: 
G\ Waites, JOS sh. Le 
